Terrorists have seized the underground control complex of a nuclear missile site, and it is up to one or two players to infiltrate the base and kill the enemy leader. Improved weapons and grenade powerups are made available within the game, either in plain sight or within crates that must be unlocked using keys. Additionally, crates may contain orbs or one of the six pieces of the Heavy Barrel superweapon.
The Heavy Barrel is found in six pieces and is an energy cannon capable of destroying any enemy in the game with a single shot (except the final enemy, and possibly one other boss that may have required two shots). The weapon has a wide arc of fire and can be fired as fast as the player's trigger finger permits, but after 30 seconds (99 in the NES version) its use is exhausted, at which point the bearer reverts to his previous weaponry.
A similar game, Midnight Resistance was released by Data East in 1990, and ported to the Sega Genesis. It was often touted as a sequel to Heavy Barrel, due to a similar control scheme (only with a side-view), graphics, and sound effects.
- BFG: The Heavy Barrel superweapon is definitely considered this. And a kickass one to boot: it is an instant kill on pretty much every enemy except the Final Boss (who doesn't last that much longer anyway).
- Bottomless Magazines: Your weak starting weapon, and the Heavy Barrel. Unfortunately, the Heavy Barrel lasts for only 30 seconds.
- Chain-Reaction Destruction: Makes one wonder what kind of explosive material are concrete walls built of.
- Degraded Boss: The second stage boss (some elevator claw machine thing) appears as a miniboss in one of the later levels. And you have to fight two of them.
- Difficulty By Console: The NES version is a lot easier then than the original arcade version.
- Disappears Into Light: Most normal soldiers die like this.
- Dolled-Up Installment: Chip and Dale 3, which is basically the NES version of Heavy Barrel except the player characters are replaced by Chip and Dale with guns!
- Elevator Action Sequence: Many of the stages feature these (in fact, pretty much all the underground ones). Stage 2 has you fight a boss during one!
- Epic Flail: The Hyper Ion Ball, a grenade substitute that whips around the user in a circle.
- Flash of Pain: Hitting stronger things brightens them up.
- IKEA Weaponry: In order to use the Heavy Barrel, you will need to obtain its six parts.
- Kill It with Fire: The flamethrower weapon, arguable the best one to beat tough enemies and bosses with (excluding the Heavy Barrel).
- More Dakka: The Heavy Barrel weapon combines this with For Massive Damage. Would be a Game Breaker, if not for the fact that you can only use it for 30 seconds.
- One-Hit Kill: The Heavy Barrel against most regular enemies.
- One-Hit-Point Wonder: Your character can only take one hit to die.
- Spread Shot: One of the improved weapons you could obtain. Getting red bombs also made your bombs explode in an eight-way burst.
- Stalked by the Bell: In the arcade version, taking too long in one area would result in multiple red bombs (which explode in a very deadly eight-way blast) continuously being thrown into the arena until you moved on or got killed. Worst of all, it can happen during the battle with the Final Boss.
- Super Mode: Partially. When you get the HEAVY BARREL!!!, your attack becomes a devastating One-Hit Kill to most enemies, but you can still be killed normally.
- The Very Definitely Final Dungeon: Normally, there are two regular background musics, one used in open air areas and another used in underground levels. You know that you're in the final stage when the background music is this.
- A Winner Is You: The ending is definitely this.
- Wolfpack Boss: The bosses of the second-to-last stage are two robotic enemies that shoot fireballs at you. Later, you have to fight against three of them.